1. Technical Field of the Invention
The present invention relates to multi-mode mobile stations operable within a telecommunications system and, in particular, to a multi-mode mobile station operable within a selected one of two or more different types of cellular telecommunications systems in instances where an inserted subscriber identity module (SIM) card includes complete communications standard required subscription information pertinent to non-selected ones of the supported types of cellular telecommunications systems.
2. Description of Related Art
Terrestrial cellular telecommunications systems are now commonly available for subscriber use in most of the major urban areas of the world. However, in spite of the success of such systems and the increasing demand for expanded coverage, there remain areas of the world where terrestrial cellular telecommunications systems do not present a commercially or economically viable communications option. For example, rural areas with low population densities do not offer a substantial enough potential subscriber base to justify the cost of installing a terrestrial cellular telecommunications system infrastructure. Notably, these rural areas sometimes lack conventional wireline (fixed) telephone service as well for the same economic reasons.
There also exist capacity concerns with respect to existing terrestrial cellular telecommunications systems. The dramatic success and acceptance of this form of telecommunications has led to increased subscription growth. With more and more users, some existing terrestrial cellular telecommunications systems have become overloaded during peak use times. While the demand justifying expansion is present, some service providers have been slow to respond by making improvements to and authorizing the expansion of the existing infrastructure. In some instances, governmental restrictions have further hampered effective service provider response to increases in demand.
The foregoing concerns have contributed towards the development of satellite cellular telecommunications systems. Such systems rely on communications satellites placed in orbit above the surface of the earth to relay telephonic communications between mobile stations (also referred to as "user terminals") and conventional terrestrial cellular and wireline telecommunications systems. The primary benefit, from both a service and cost perspective, provided by a satellite cellular telecommunications system is that a single satellite is capable of servicing the telecommunications needs of many users distributed over a substantial service area including both rural and urban areas. In fact, one satellite may be capable of providing telecommunications service throughout an entire country. Satellites are further capable of providing telecommunications service in areas of the world (like the ocean surface and remote mountain ranges) where installation of conventional terrestrial cellular and wireline telecommunications system infrastructure is difficult if not impossible.
It is well known that the terrestrial cellular telecommunications system and the satellite cellular telecommunications system operate in accordance with different communications standards. Furthermore, many different types of terrestrial cellular telecommunications systems exist, again each operating in accordance with different communications standards. Thus, for example, a subscriber wishing to access and use the Asia Cellular Satellite (ACeS) type satellite cellular telecommunications system must possess and utilize a mobile station configured for operation in accordance with the ACeS communications standard. If that same subscriber wanted to access and use the Global System for Mobile (GSM) communications type terrestrial cellular telecommunications system, their mobile station must be configured for operation in accordance with the GSM communications standard. Similarly, the mobile station must be appropriately configured for operation in any other desired terrestrial or satellite cellular telecommunications system (such as, an I-CO type satellite cellular telecommunications system, or the Advanced Mobile Phone System (AMPS or D-AMPS) type or Personal Communications System (PCS) type terrestrial cellular telecommunications systems).
Recent developments in mobile station design have made multi-mode mobile stations available for subscriber use. Such multi-mode devices are capable of being configured for operation in any selected one of two or more available cellular telecommunications system types. For example, the mobile station may be terrestrial system oriented and configured for operation in one mode in accordance with the GSM communications standard, and in another mode in accordance with the PCS communications standard. With the advent of satellite cellular telecommunications systems, increasing numbers of mobile stations are capable of operation in one of the terrestrial cellular telecommunications systems, such as GSM, and one of the satellite cellular telecommunications systems, such as ACeS. Access to such a mobile station, in conjunction with the placement into operation of both terrestrial and satellite cellular telecommunications systems, advantageously provides the subscriber with access to telecommunications services substantially throughout the entire world.
The communications standard required subscription information necessary for specifying proper multi-mode mobile station operation in one of several available types of terrestrial or satellite cellular telecommunications systems is conventionally stored in a subscriber identity module (SIM) card which is inserted into the mobile station. Beyond being a central store of subscriber information, the primary advantage provided by the SIM card is that a subscriber and his or her subscription are no longer tied (or assigned) to a particular mobile station. The subscriber instead may insert their personal SIM card into any SIM supporting mobile station and immediately have access to their subscription to make and receive cellular telephone calls.
Instances are likely to occur where a multi-mode mobile station is capable of operation in a particular type of terrestrial or satellite cellular telecommunications system, and the subscriber in fact desires to communicate over that particular system, but the inserted SIM card does not include the particular communications standard required subscription information necessary for specifying proper multi-mode mobile station operation in that system. For example, the multi-mode mobile station may be capable of operation in both the ACeS type satellite cellular telecommunications system and the GSM type terrestrial cellular telecommunications system. However, the inserted subscriber SIM card may include communications standard required subscription information relating only to operation in accordance with the GSM type terrestrial cellular telecommunications system. Certain ACeS communications standard subscription information is missing from, or has no equivalent in, the available GSM communications standard required subscription information. Accordingly, if no GSM type terrestrial cellular telecommunications system is available to the subscriber at a given location, and even though the ACeS type satellite cellular telecommunications system is available for mobile station access, the failure of the SIM card to include the ACeS communications standard required subscription information would preclude mobile station operation over that satellite cellular telecommunications system.
There is a need then for a multi-mode mobile station to support full multi-mode operation over and access to various types of terrestrial and satellite cellular telecommunications systems even in those instances where a subscriber inserted SIM card fails to include the terrestrial and satellite communications standard required subscription information necessary for such operation.